1. Field of the Invention
The invention relates to a self-propelled loader especially adapted to working in confined spaces such as load transfer yards for logs, lumber and the like. In particular, the invention comprises a self-propelled knuckle boom loader having a tricycle wheel arrangement, with two drive wheels driven hydraulically from the hydraulic system of the loader, and a freewheeling third wheel forming a caster that is lifted from the ground when the loader is attached to a hitch-for trailering.
2. Description of the Prior Art
Turntable mounted hydraulic loaders are known in the art, including knuckle boom loaders having a grasping or other cargo-engaging mechanism at the end of an articulated boom. Loaders of this type conventionally are mounted on the platform of a truck, such as at an end or corner of a flatbed of a truck, where the loader can be used to move cargo on and off the truck bed. A larger form of loader or crane can occupy all the space on the truck bed, for use in moving cargo from one place to another on the ground, to move cargo between a truck or rail car and the ground, etc. It is also possible to provide a loader or crane on a trailer that can be towed by a tractor. Frequently, loaders as so mounted are provided with hydraulically operable outriggers that can be lowered to stabilize the loader and to prevent the vehicle from upsetting, should the loader engage a substantial weight at a point cantilevered from the truck or trailer.
One drawback of these arrangements is that if the loader is to be used at different locations, the truck or tractor is practically dedicated to use with the loader. In conjunction with yard work, it is important that the loader be transportable from place to place, often frequently, to reach and move items. Where the loader is mounted on and/or movable only by a truck, the engine, cab accoutrements, controls, and supporting structure of the truck are needed. It is possible to have one worker operate the loader and another to drive the truck. To a large extent, these elements and workers are duplicated on the truck and on the loader, which is redundant and wastes money.
Typically, the operator of a truck mounted loader is also the operator of the truck. However, to relocate the loader the operator must leave the controls of the loader, move to the cab of the truck, drive the truck to the new location and then return to the controls of the loader, which wastes time.
Arrangements involving a loader on a truck are clumsy to use in narrow operating areas, such as, for example, between piles of logs in lumber yards. Trucks or tractortrailer arrangements necessarily have a relatively long turning radius, and to use a loader on a truck it is necessary to leave sufficient space in the yard to maneuver the truck, which wastes space. In addition, the position of the truck or trailer cab can prevent the knuckle boom from having a full 360.degree. operating range of motion. This operational limitation necessitates more frequent moving of the entire arrangement to reach items forward of the truck cab.
A smaller, more easily maneuverable hydraulic loader system would permit more efficient use of storage space, for example in lumber yards, where large objects must be moved from place to place. Self-propelled cranes and the like of course are well known, and typically have wheels or tracks. However, conventional self-propelled devices of this type are not readily transported over the road. The ground-engaging propulsion mechanisms (e.g., hydraulically driven wheels or tracks) are designed for slow movement over rough terrain, steep slopes, etc., rather than for highway use. Adapting such mechanisms for highway use would detract from their effectiveness off the road.
It would be advantageous if the conflicting needs associated with operation as a loader, and with transportation (both on and off the road) could be resolved in an optimal manner. There is a need for an easily maneuverable, hydraulic loader that does not require a dedicated truck or tractor and can be controlled directly from the loader controls, which is readily transportable both in a highly maneuverable manner over rough terrain and between obstacles as typical of a yard, and which is also optimized for transport over the road.